The present invention relates to a surface emitting device for use in a liquid crystal display unit or the like.
A surface emitting device has been proposed as a device for illuminating a liquid crystal display panel or the like. The surface emitting device is called a front light or a back light. The surface emitting device is generally formed in such a manner that a light source is provided on a side face of a light guide plate made of a transparent substrate to introduce light into the light guide plate, and the introduced light is diffused by a reflection portion provided on a surface of the light guide plate, so that the surface emitting device attains face emission. As a typical reflection portion, for example, it has been proposed that fine prism grooves about 10 μm wide or the like are provided.
On the other hand, prism grooves or the like may be contaminated due to fine dust or the like deposited on the prism grooves. Such contamination has influence on the reflection of light from the light source on the prism grooves or the like. Thus, there is a problem that desired surface emission is impeded. Therefore, for example, Japanese Patent Laid-Open No. 2001-133775 proposes that the light guide plate surface is covered with a dustproof cover.
However, when the dustproof cover disclosed in the official gazette is used, there is a gap between the dustproof cover and the light guide plate surface so that the device as a whole is increased in thickness. Thus, a request to make the device thinner cannot be satisfied sufficiently.